The invention is directed to an arrangement for protecting electrical installations against electromagnetic disturbances, especially against excess voltages and the effects of lightning, which arrangement uses metallic shielding which embraces the electrical lines laid between individual electrical apparatus and which is in electrical connection with charge eliminator points.
Arrangements of this type are especially required in aircraft where large quantities of electrical apparatus with very different useful information signals and disturbance sensitivities are arranged in a relatively confined space and where the possibility of mutual interaction must be reliably eliminated; moreover, this electrical equipment is greatly endangered in its safe operation by the effects of a lightning strike on the electronic apparatus. Because of this, an already known method is to equip electrical connecting cables in aircraft, especially complete cable harnesses, with shielding from metallic conducting material, and to connect this shielding respectively at its ends with the housings of the electrical apparatus or with specially provided leads to an electrical ground.
Generally, a hose-shaped braiding consisting of individual metal strands is utilized for this purpose, which is connected with a metallic connector at the cable ends. The connection of this braiding with provided charge elimination points frequently occurs also by means of separate hose-type clamps, which surround the braiding at the cable ends and from which a separate line, which is also designated as a "pig-tail," leads to the charge elimination point.
A disadvantage of such known shielding arrangements is that, because of the free or uncovered areas remaining in the braiding, the penetration of disturbance fields, especially with the high excess voltages occurring in a lightning strike, cannot be reliably eliminated. Furthermore, a problem often occurring with these known devices is that the plug and socket connections used as connector elements for the braiding consist of aluminum materials and tend to corrode, thus entailing malfunctions. Finally, a disadvantage of this known arrangement can be seen in the circumstance that the lines laid inside of such shielding are only accessible with great difficulty from outside in case of a defect, whereby a possibly required repair or replacement of a defective lead involves considerable expense.